Thermoplastic polyester resins such as polybutylene terephthalate resins and polyethylene terephthalate resins have been extensively used as materials for mechanical elements such as bearings and gears because of good mechanical strength and wear resistance thereof. However, these thermoplastic polyester resins fail to exhibit sufficient friction and wear characteristics when used singly. Therefore, solid lubricants such as graphite, molybdenum disulfide and tetrafluoroethylene resins, lubricating oil agents such as mineral oils and waxes, or other low-frictional synthetic resins such as polyethylene resins are added to the thermoplastic polyester resins in order to enhance friction and wear characteristics thereof.
For example, there have been proposed the resin compositions which are composed of a polybutylene terephthalate resin and a specific amount of calcium stearate, and exhibit an excellent moldability (refer to Japanese Patent Application Laid-Open (KOKAI) No. 51-114454(1976)). Also, there have been proposed the resin compositions which are composed of a polyethylene terephthalate resin, a neutral or partially neutralized montan wax salt or montan wax ester salt and glass fibers, and exhibit an excellent moldability (refer to Japanese Patent Publication (KOKOKU) No. 58-46150(1983)). In addition, there have been proposed the thermoplastic resin compositions which are obtained by melt-kneading a thermoplastic resin selected from the group consisting of polyamide resins, polyacetal resins, polyester resins and polycarbonate resins with a specific ultra-high molecular weight polyethylene resin powder, and exhibit excellent impact resistance and wear resistance (refer to Japanese Patent Publication (KOKOKU) No. 63-65232(1988)).
In recent years, with the progress of OA equipments such as copying machines, it has been required to reduce the weight of mechanical apparatuses and devices used therein. For this reason, as a material of a mating member for the sliding member, there have been used aluminum alloys. In the case of sliding members such as bearings, etc., materials, surface properties or the like of the mating member are important factors for attaining excellent friction and wear characteristics of the sliding members.
However, the sliding members produced from the resin compositions described in the above patent documents have such a problem that when used together with a mating member composed of aluminum alloys, a coefficient of friction thereof is high, and a wear amount thereof is large. Also, the surface of the mating member composed of aluminum alloys tends to be severely damaged depending upon use conditions thereof. Accordingly, it has been demanded to provide a sliding member exhibiting good friction and wear characteristics even when used together with a mating member composed of a soft metal such as aluminum alloys.